Insulating mount structure, insulation monitoring system, and insulation monitoring method for fuel cells

ABSTRACT

An insulating mount structure for a fuel cell, which includes insulating mounts ( 2 ) for mounting the fuel cell stack ( 1 ) on a grounded structure ( 7 ), and a water barrier ( 3 ) extending in a space between the fuel cell a stack ( 1 ) and the grounded structure ( 7 ), being electrically isolated from both of the fuel cell ( 1 ) and the grounded structure ( 7 ). The water barrier ( 3 ) is formed in a container shape having an opening ( 3   a ) on upper side thereof.

TECHNICAL FIELD

The present invention relates to an insulating mount structure for fuelcells, a system for monitoring insulation status thereof, and a methodfor monitoring the same.

BACKGROUND ART

Fuel cells or a fuel cell stack are required, in practical use, to beisolated electrically from a surrounding structure thereof.

Japanese Patent Application Laid-Open Publication No. 2002-367651discloses an insulating mount for electrically isolating a fuel cellstack inside a housing thereof. The insulating mount has an insulatorprovided between mounting bolts and the bottom wall of the housing.

DISCLOSURE OF INVENTION

However, in the above-mentioned insulating mount, in case cooling waterleaks from the fuel cell stack and builds up in the housing, themounting bolts and the insulators are submerged in the water, resultingin a failure in maintaining insulation between the fuel cell stack andthe housing thereof.

The present invention was made in the light of the problem. An object ofthe present invention is to provide: an insulating mount structure forfuel cells, which prevents mounting bolts thereof from being submergedin cooling water and the like leaked from the fuel cells, and maintainsthe fuel cells insulated; a system for monitoring insulation statusthereof; and a method for monitoring the same.

An aspect of the present invention is an insulating mount structure fora fuel cell, comprising: an insulating mount for mounting the fuel cellon a grounded structure; and a barrier extending in a space between thefuel cell and the grounded structure, and being electrically isolatedfrom the fuel cell and the grounded structure, the barrier having acontainer shape with an opening on upper side thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the accompanyingdrawings wherein:

FIGS. 1A and 1B show an insulating mount structure for fuel cellsaccording to a first embodiment of the present invention, FIG. 1A beinga sectional view taken along a line IA-IA in FIG. 1B, and FIG. 1B beinga sectional view taken along a line IB-IB in FIG. 1A;

FIGS. 2A and 2B show an insulating mount structure for fuel cellsaccording to a second embodiment of the present invention, FIG. 2A beinga sectional view taken along a line IIA-IIA in FIG. 2B, and FIG. 2Bbeing a sectional view taken along a line IIB-IIB in FIG. 2A;

FIG. 3 shows a configuration of an insulation monitoring systemaccording to a third embodiment of the present invention;

FIG. 4 is a flowchart showing a general control flow of the system inFIG. 3; and

FIG. 5 is a flowchart showing control processing in a controller of thesystem in FIG. 3.

BEST MODES FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be explained below withreference to the drawings, wherein like members are designated by likereference characters.

First Embodiment

An insulating mount structure according to a first embodiment of thepresent invention is, as shown in FIGS. 1A and 1B, constituted of a fuelcell stack 1, insulating mounts 2, and a water barrier 3.

The fuel cell stack 1 is fixed to an electrically grounded structure 7,being supported, at four corners of the bottom face thereof, on theinsulating mounts 2 which are mounting brackets on which insulatingprocessing or treatment has been performed.

The water barrier 3 is formed to extend in a space between the fuel cellstack 1 and the grounded structure 7, and to have a container-like shapewith an opening 3 a at the top thereof. The fuel cell stack 1 is placedtherein and surrounded by sidewalls 3 b of the water barrier 3.

Specifically, the fuel cell stack 1 is fixed to the water barrier 3,being supported by upper mounts 2 b of the insulating mounts 2, whichare provided at four corners of the bottom face of the fuel cell stack 1between the bottom face thereof and the upper face of the bottom of thewater barrier 3. The water barrier 3 is fixed to the structure 7, beingsupported by lower mounts 2 a of the insulating mounts 2, which areprovided between the bottom face of the water barrier 3 and thestructure 7 at four locations corresponding to the upper mounts 2 a.Thus, the fuel cell stack 1, water barrier 3 and structure 7 areseparated from and not in contact with each other, whereby thesecomponents are electrically insulated from each other. Hereinafter, anassembly of the combined fuel cell stack 1, mounts 2 and water barrier 3will be called as an insulated fuel cell assembly FCA.

According to the first embodiment, even when water, such as reactionwater generated by electrochemical reaction in the fuel cell stack 1 orcooling water thereof, leaks from the fuel cell stack 1, the water iscollected and held in the space between the water barrier 3 and the fuelcell stack 1, being prevented from flowing out of the water barrier 3 tothe structure 7. Therefore, the lower mounts 2 a between the structure 7and the water barrier 3 will not be submerged in water and maintaineddry, and the insulation between the grounded structure 7 and theelectrically neutral water barrier 3 is secured, unless the watercollected inside the water barrier 3 builds up and the level of thecollected water reaches a height H1 of the sidewall 3 b thereof.

Meanwhile, even when water enters inside the structure 7 due to waterinvasion from outside or the like, the water is accumulated in the spacebetween the water barrier 3 and the structure 7, being prevented fromflowing into inside the water barrier 3. Therefore, the upper mounts 2 bbetween the water barrier 3 and the fuel cell stack 1 will not besubmerged in water and maintained dry, and the insulation between thefuel cell stack 1 and the water barrier 3 is secured, unless the wateraccumulated outside the water barrier 3 builds up and the level of theaccumulated water reaches the top edge at a height H2 of the opening 3 aof the water barrier 3.

Second Embodiment

An insulating mount structure according to a second embodiment of thepresent invention is, as shown in FIGS. 2A and 2B, constituted of aninsulated fuel cell assembly FCA (a fuel cell stack 1, mounts 2, and awater barrier 3) and an electrically grounded fuel cell housing 4 whichhouses the insulated fuel cell assembly FCA therein.

The housing 4 constitutes a ventilated housing for FCA with an airintake pipe 5 and an air discharge pipe 6 connected at opposingpositions on the opposing sidewalls thereof. To be more specific, a vent5 a (first opening) of the air intake pipe 5 and a vent 6 a (secondopening) of the air discharge pipe 6 are provided at positions oppositeto each other on the inner faces of the sidewalls of the fuel cellhousing 4. Arrows in FIGS. 2A and 2B indicate the flowing directions ofair intake and discharge.

As in the case of the first embodiment, the fuel cell stack 1 is fixedinside the fuel cell housing 4 to a bottom wall 4 a thereof, beingsupported on the insulating mounts 2. The water barrier 3 is supportedby the mounts 2 in an electrically neutral state, and encloses the fuelcell stack 1 inside. In other words, the fuel cell stack 1, waterbarrier 3 and fuel cell housing 4 are separated from and not in contactwith each other, whereby these components are electrically insulatedfrom each other. A height H2 from the bottom wall 4 a of the fuel cellhousing 4 to the top edge of an opening 3 a of the water barrier 3 islarger than a height H3 of the top edges of the vents 5 a and 6 a on thesidewalls of the fuel cell housing 4.

According to the second embodiment, the top edge of the opening 3 a ofthe water barrier 3 is higher than the top edges of the vents 5 a and 6a, and sidewalls 3 b of the water barrier 3 are extended to cover thevents 5 a and 6 a. Therefore, even when water and the like enters fromoutside through the air intake pipe 5 and the air discharge pipe 6 intothe fuel cell housing 4, the inflowing matters or objects are blocked bythe sidewalls 3 b without wetting the fuel cell stack 1, wherebycorrosions of or failures in the fuel cell stack 1 can be prevented.Only one of the vents 5 a and 6 a, for example, the vent 5 a of the airintake pipe 5, through which the inflowing matters or objects enter morelikely than the other vent 6 a, may be positioned lower than the topedge at height H2 of the sidewall 3 b of the water barrier 3.

Third Embodiment

As shown in FIG. 3, a system for monitoring an insulation statusaccording to a third embodiment of the present invention includes: aninsulated fuel cell assembly FCA; a fuel cell housing 4; a sensor 8which measures the electrical potential of the fuel cell housing 4; asensor 9 which measures the electrical potential of a water barrier 3; asensor 10 which measures the electrical potential of the fuel cell stack1; and a controller 11 for processing data from the respective sensors8, 9 and 10.

A description will be given of a system control flow and of controlprocessing in the controller 11 with reference to FIGS. 4 and 5.

First, data of electrical potentials measured by the respective sensors8, 9 and 10 are read into the controller 11, and comparisons are made inthe controller 11 between a measured value V8 from the sensor 8 and ameasured value V9 from the sensor 9 and between the measured value V9from the sensor 9 and a measured value V10 from the sensor 10,respectively. When an absolute value |V9−V8|, the potential differencebetween the measured values V8 and V9, is equal to or below a firstpreset value PV1, which means the measured values V8 and V9 aresubstantially the same, it is determined that the fuel cell housing 4and the water barrier 3 are electrically continuous through wateraccumulated in the space therebetween, and water or the like has invadedthe fuel cell housing 4 from outside. Meanwhile, when an absolute value|V10−V9|, the potential difference between the measured values V9 andV10, is equal to or below a second preset value PV2, it is determinedthat the water barrier 3 and the fuel cell stack 1 are electricallycontinuous through water collected in the space therebetween, and waterleakage from the fuel cell stack 1 has occurred. Next, when it isdetermined that water has invaded from outside, the user is alerted by ayellow indicating lamp 12. When it is determined that water leakage fromthe fuel cell stack 1 has occurred, the user is alerted by a redindicating lamp 13 which gives advice to shut down the operation of thefuel cell stack 1, and the power of the fuel cell stack 1 is thengradually reduced. Moreover, when water leakage from the fuel cell stack1 is detected while the yellow indicating lamp 12 is on, or, when waterinvasion from outside is detected while the red indicating lamp 13 ison, the fuel cell stack 1 is shut down after or at the same time as theuser is alerted by a buzzer 14. The respective preset values PV1 and PV2can be arbitrarily set, and are preferably such values as tosubstantially meet the measured values V8, V9 and V10 from therespective sensors 8, 9 and 10. Moreover, the first and second presetvalues PV1 and PV2 may be set at the same value.

More specifically, the above control flow is realized by repeating thecontrol processing shown in FIG. 5 at regular intervals in thecontroller 11.

The measured values V8, V9 and V10 from the respective sensors 8, 9 and10 are read into the controller 11 in Step 51, and it is determinedwhether the absolute value |V9−V8|, the difference between the measuredvalues V8 and V9, is equal to or below the first preset value PV1 (Step52). Then, it is determined whether the absolute value |V10−V9|, thedifference between the measured values V9 and V10, is equal to or belowthe second preset value PV2 (Step 53 or 54). If |V9−V8| is determined tobe equal to or below the PV1 (Step 52) and |V10−V9| is determined not tobe equal to or below the PV2 (Step 53), the yellow indicating lamp 12 isturned on (Step 55) to alert the user to water invasion from outside. If|V9−V8| is determined not to be equal to or below the PV1 (Step 52) and|V10−V9| is determined to be equal to or below the PV2 (Step 54), thered indicating lamp 13 is turned on (Step 56) to alert the user tooccurrence of water leakage from the fuel cell stack 1, and thus thepower of the fuel cell stack 1 is gradually reduced (Step 57). If|V9−V8| is determined to be equal to or below the PV1 (Step 52) and|V10−V9| is determined to be equal to or below the PV2 (Step 53), analarm is given by means of the buzzer 14 (Step 58) and the fuel cellstack 1 is shut down (Step 59). If |V9−V8| is not equal to or below thePV1 (Step 52) and |V10−V9| is not equal to or below the PV2 (Step 54),operation of the fuel cell stack 1 is continued.

According to the third embodiment, by monitoring the potential of thefuel cell stack 1, water barrier 3 and fuel cell housing 4, waterleakage from the fuel cell stack 1 can be detected when the potentialdifference V10−V9 between the fuel cell stack 1 and the water barrier 3reaches or is approaching the preset value PV2. Moreover, when thepotential difference V9−V8 between the water barrier 3 and the fuel cellhousing 4 reaches or is approaching the preset value PV1, water invasionfrom outside can be detected. Furthermore, even when there is waterinside the fuel cell housing 4, if it is judged that the water hasinvaded the fuel cell housing 4 from outside and is accumulated outsidethe water barrier 3, operation of the fuel cell stack 1 can be continuedas long as the insulation thereof can be maintained.

The preferred embodiments described herein are illustrative and notrestrictive, and the invention may be practiced or embodied in otherways without departing from the spirit or essential character thereof.The shape of the fuel cell housing 4, the positions of the vents 5 a and6 a where the air intake pipe 5 and the air discharge pipe 6 areattached to the housing 4, the position(s) and the number of themount(s) 2, the shape of the water barrier 3, etc. can be freely setwithout departing from the effects of the embodiments. The scope of theinvention being indicated by the claims, and all variations which comewithin the meaning of claims are intended to be embraced herein.

The present disclosure relates to subject matters contained in JapanesePatent Application No. 2003-144612, filed on May 22, 2003, and JapanesePatent Application No. 2003-426195, filed on Dec. 24, 2003, thedisclosure of which are expressly incorporated herein by reference intheir entirety.

INDUSTRIAL APPLICABILITY

In an insulating mount structure of the present invention, a waterbarrier enclosing a fuel cell stack is provided in the space between thefuel cell stack and a grounded structure, being electrically isolatedfrom both of the fuel cell stack and the structure. Accordingly, evenwhen water generated in the fuel cell stack, cooling water thereof andthe like leak from the fuel cell stack inside the water barrier, thewater is collected and held inside the water barrier, and insulatingmounts supporting the water barrier on the grounded structure ismaintained dry. Therefore, the present invention can be utilized tomaintain insulation between fuel cells and its surrounding structure.

1. A fuel cell assembly comprising a fuel cell and an insulating mountstructure for the fuel cell, comprising: an insulating mount formounting the fuel cell on a grounded structure; and a barrier extendingin a space between the fuel cell and the grounded structure, and beingsupported by the insulating mount and held in the space in a spacedposition, the barrier being electrically isolated from the fuel cell andthe grounded structure, the barrier having a container shape with anopening on an upper side thereof.
 2. A fuel cell assembly comprising theinsulating mount structure according to claim 1, wherein the barrier hasa sidewall surrounding the fuel cell.
 3. A fuel cell assembly comprisingthe insulating mount structure according to claim 2, wherein thegrounded structure comprises a housing of the fuel cell.
 4. A fuel cellassembly comprising the insulating mount structure according to claim 3,wherein the housing is provided with a first opening to bring outsideair into the housing and a second opening to discharge air inside thehousing to outside.
 5. A fuel cell assembly comprising the insulatingmount structure according to claim 4, wherein a top edge of the sidewallof the barrier is positioned higher than the first opening of thehousing.
 6. A fuel cell assembly comprising the insulating mountstructure according to claim 1, wherein the insulating mount comprisesan upper insulating mount and a lower insulating mount, and the barrieris sandwiched between and supported by the upper insulating mount andthe lower insulating mount.
 7. An insulation monitoring system for afuel cell, comprising: an insulating mount for mounting the fuel cell ona grounded structure; a barrier extending in a space between the fuelcell and the grounded structure, and being supported by the insulatingmount and held in the space in a spaced position, the barrier beingelectrically isolated from the fuel cell and the grounded structure, thebarrier having a container shape with an opening on an upper sidethereof; a first sensor configured to measure potential of the groundedstructure; a second sensor configured to measure potential of thebarrier; a third sensor configured to measure potential of the fuelcell; and a controller configured to judge that water has invaded fromoutside when a difference between the potential measured by the firstsensor and the potential measured by the second sensor is within a firstrange, and that water is leaking from the fuel cell when a differencebetween the potential measured by the second sensor and the potentialmeasured by the third sensor is within a second range.
 8. An insulationmonitoring method for a fuel cell, comprising: having an open-topcontainer-shaped barrier supported and mounted in a first spacedposition on a grounded structure by a first insulating mount; having afuel cell supported and mounted in a second spaced position inside thebarrier by a second insulating mount; measuring potential of thegrounded structure; measuring potential of the barrier; measuringpotential of the fuel cell; monitoring a difference between thepotential measured for the grounded structure and the potential measuredfor the barrier; and monitoring a difference between the potentialmeasured for the barrier and the potential measured for the fuel cell.9. A fuel cell assembly comprising the insulating mount structureaccording to claim 1, wherein the barrier is solid material capable ofhaving an electrical potential.
 10. A fuel cell assembly comprising theinsulating mount structure according to claim 1, wherein the barrier isheld in the space at a first spaced distance from the fuel cell and asecond spaced distance from the grounded structure.
 11. A fuel cellassembly comprising the insulating mount structure according to claim 1,wherein the opening of the container shape of the barrier is formed bysidewalls positioned at a spaced distance from the fuel cell.
 12. A fuelcell assembly comprising the insulating mount structure according toclaim 1, wherein the barrier does not contact the fuel cell and does notcontact the grounded structure.
 13. The insulation monitoring systemaccording to claim 7, wherein the barrier is solid material capable ofhaving an electrical potential.
 14. The insulation monitoring systemaccording to claim 7, wherein the barrier is held in the space at afirst spaced distance from the fuel cell and a second spaced distancefrom the grounded structure.
 15. The insulation monitoring systemaccording to claim 7, wherein the opening of the container shape of thebarrier is formed by sidewalls positioned at a spaced distance from thefuel cell.
 16. The insulation monitoring system according to claim 7,wherein the barrier does not contact the fuel cell and does not contactthe grounded structure.
 17. The insulation monitoring method accordingto claim 8, wherein the barrier is solid material capable of having anelectrical potential.
 18. The insulation monitoring method according toclaim 8, wherein the barrier is mounted in the first spaced position ata first spaced distance from the grounded structure, and wherein thefuel cell is mounted in the second spaced position at a second spaceddistance from the barrier.
 19. The insulation monitoring methodaccording to claim 8, wherein the open-top of the container-shapedbarrier is formed by sidewalls positioned at a spaced distance from thefuel cell.
 20. The insulation monitoring method according to claim 8,wherein the barrier does not contact the fuel cell and does not contactthe grounded structure.
 21. A fuel cell assembly comprising theinsulating mount structure according to claim 1, wherein the barrier isheld in the space at a spaced distance from the grounded structure bythe insulating mount.
 22. The insulation monitoring system according toclaim 7, wherein the barrier is held in the space at a spaced distancefrom the grounded structure by the insulating mount.
 23. The insulationmonitoring method according to claim 8, wherein the barrier is held inthe space at a spaced distance from the grounded structure by the firstinsulating mount.